Displaying Dates and Time with Locally Relevant Time Zone Information

Question

I am specifying enhancements to a system that will need to report on employee activity in different time zones.

I anticipate that users of the system will be able to set a 'Home' or Local Time Zone - and I think that the reports and UI will be most understandable if the user sees the local time of the event, wherever that event happened.

However, I do not want to obscure the fact that some times pertain to a different time zone. Let's just assume for a moment that I want to display a 09:00 start time for employee A in Athens Greece, employee B in London England, and employee C in New York USA, and I am in New York. This example uses offsets relative to New York

A:  09:00 +07:00
B:  09:00 +05:00
C:  09:00

I believe that this solution would be relatively easy to implement using DateTimeOffset types in Sql Server and .Net, but I am uncomfortable about it because it kind-of looks like a ISO8601 format, but it definitely is not that, as the hour offsets are relative to New York, not relative to UTC.

Perhaps instead of using hours offset we could specify a time zone instead:

A:  09:00 [EET]
B:  09:00 [UTC]
C:  09:00

The concern I have with this solution is that DateTimeOffset and such only store an hour-offset, and do not store this time zone information... and it may be non-trivial to discover which actual time zone the event was in later on (consider Daylight Saving Time changes).

Bear in mind employee A might be in Athens one day, and Berlin the next, and so we can not assume on that being fixed, or decide to exclude 'non-home' data from a report.

While I am most interested in the display format others would suggest for this situation; one caveat is that the solution must be fairly easy to implement and quick to process.

Answer 1

Mobile apps have the benefit of utilizing geo-location data to exactly determine where the user is at, converting times relative to the time zone they are in.

With websites, most of the time you see options for users to expressly state what their preferred time zone is. The onus falls upon the user to change their time zone if they wish.

You could provide a microinteraction loop that seeks to determine the user's location based on their IP address. If the address is resolving outside of their stated time zone, you could provide a small tooltip stating the potential problem: "It looks like you're not currently in [STATED HOME TIME ZONE]." Then offer a resolution such as, "Change time to [CURRENT TIME ZONE]."

Here's a sample tooltip from Gmail:

Answer 2

In the end the client has chosen to aim for the use of Time Zone abbreviations where they are necessary (i.e. not in the current time zone)

A:  09:00 [EET]
B:  09:00 [UTC]
C:  09:00

While users of this UX forum may not care too much about implementation details, this means we won't be using DateTimeOffset as the underlying type to store international times. We have decided to store local times, with a TimeZoneId which will tell us how many hours from UTC the time was. This will make comparisons of absolute times harder, but will provide what we think will be a good 'natural' way to view time for the majority of interface elements.